Flexible, multi-layered, fiber-containing articles, and especially flexible ballistic resistant articles such as bulletproof vests, raincoats, curtains and blankets containing high strength fibers are known. Fibers conventionally used in forming flexible multi-layered fiber-containing articles include aramid fibers such as poly (phenylenediamine terephthalamide), nylon fibers, glass fibers, metal fibers and the like. In articles such as bulletproof vests or parts of vests, the fibers are ordinarily arranged in a network, such as a woven or a knitted fabric.
A number of properties are generally considered to be necessary for high strength fiber to be useful as a component of a ballistic resistant article. Four of these factors, listed by John E. E. Hansen and Roy C. Laible in a paper presented at the "Fiber Frontiers" ACS Conference, June 10-12, 1974 entitled "Flexible Body Armor Materials," are high modulus, high melting point, high strength and/or work-to-rupture values, and high resistance to cutting or shearing. With regard to melting point, in "the Application of High Modulus Fibers for Ballistic Protection," R. C. Laible et al., J. Macromel. Sci. Chem., A7(1), pp. 295-322, 1973, at p. 298, it is disclosed that fiber material must have a high degree of heat resistance to be useful as a ballistic resistant article; for example, a polyamide material with a melting point of 255.degree. C. was deemed to possess better ballistic impact resistance properties than did a polyolefin fiber with equivalent tensile properties but a lower melting point. Consequently, today's soft armor (e.g., bulletproof vests and raincoats) is essentially formed from high melting point materials, predominantly aramid fibers.
Notwithstanding the required properties noted above, U.S. Pat. Nos. 4,403,012 and 4,457,985 disclose flexible ballistic resistant articles such as vests comprising networks of high molecular weight polyolefin fibers, and rigid and semi-rigid ballistic articles comprising composites including such fibers embedded in different matrices (such as olefin polymers and copolymers, unsaturated polyester resins, epoxy resins, and other resins curable below the melting point of the fiber). The products disclosed in these patents possess superior ballistic resistance as compared to the ballistic resistance of articles composed of aramid fibers.
We have discovered improved flexible multi-layered articles which possess unexpectedly superior ballistic resistant properties as compared to prior art armor products.